Circuit breaker mechanism



R. 'STEINER CIRCUIT BREAKER MECHANISM May 14, 1957 4 Sheets-Sheet 1 Filed July 7, 1954 rullll I INVENTOR RUDOLF STEINER BY ATTORNEYS May 14, 1957 R. STEINER CIRCUIT BREAKER MECHANISM 4 Sheets-Sheet 2 Filed July '7, 1954 INVENTOR.

F. A v:

D N on S F T y14, 1957 RSTEINER 2,792,470

CIRCUIT BREAKER MECHANISM Filed July '7, 1954 4 Sheets-Sheet 3 INVENTOR. RUDOLF STEI NER A TTORNEYS y 4, 1957 R. STEINER 2,792,470

CIRCUIT BREAKER MECHANISM Filed July 7, 1954 4 Sheets-Sheet 4 "OFF"! "ON ll INVENTOR. RUDOLF STEINER A TTOR/VEYS United States Patent 2,792,470 CHQCUIT BREAKER MEtZHANISM Rudolf Steiner, Levittown, Pm, assigner to Harry Wib hams Manufacturing Company, Chicago, iii, a corporation of Illinois Application July 7, 54, Serial No. 541,5951 10 Claims. (Cl. Edd-106) (Granted under Title U. S. Code (1952), see. 2-65) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

The present invention relates to a circuit breaker mechanism and more particularly to a circuit breaker mechanism in which all movable parts are either individually balanced or else shaped and pivoted in such a manner that they tend to secure stable positions under adverse physical conditions such as severe vibration or shock loads. In addition, the circuit breaker mechanism comprising the instant invention includes a movable contact element which is completely disconnected from the other movable elements of the mechanism Whenever the circuit breaker is opened either manually or automatically.

The various different types of circuit breaker mechanisms now in existence are characterized by at least one and generally several of the following undesirable featur s. in most circuit breaker mechanisms the manual actuator is generally an integral portion of the mechanism so arranged in relation to other parts thereof that it is not readily rcplaceable by another actuator of another design or type more desirable or suitable in certain applications. The automatically operable sensing means, and particularly a thermal sensing means, is generally incorporated in the mechanism as an integral part thereof or of the mechanism lock, so that the particular type of sensing means cannot readily be replaced by another type hich may be more desirable in a particular application. I n many circuit breaker mechanisms the movable contacts are arranged so that they drag a part or all of the mechanism along, particularly during the contact opening movement, with the result that a retarding effect is im posed upon the movement of the movable contacts, which is inherently antagonistic to the necessity for rapid displacement of the movable contacts to avoid the adverse effects of arcing. Most circuit breaker mechanisms engage the movable contact element at a point near the pivotal support about which the contact element moves, thus establishing an unfavorable relationship between the related parts which results in undesirable locking qualities when the mechanism is placed in the on position. Many circuit breakers provide for positive make or for positive break, but few circuit breaker mechanisms offer both of these desirable features. Almost all known types of circuit breaker mechanisms have unbalanced movable parts with inherent characteristics which invite unreliable settings of these parts particularly when the mechanism is exposed to severe vibration or shock load conditions. in numerous instances attempts have been made to overcome this serious deficiency by the incorporation of artificially counter-balanced parts. However, this remedy inevitably results in the undesirable addition of a substantial amount of dead weight to the circuit breaker mechanism. Moreover, the conversion of existing single-pole circuit breaker mechanisms to multi-pole units usually requires major redesign of the mechanism at the expense of desirable features originally incorporated in the single-pole assembly. Finally, the release or trip portion of known types of eircut breaker mechanisms generally includes one or more parts involving exceedingly close tolerances in order to insure proper operation of the mechanism. Consequently, the fabrication of such parts is relatively difficult and they must be specially treated to eliminate excessive wear at critical points due to the relatively large forces exerted within the mechanism.

The present invention contemplates a circuit breaker mechanism incorporating numerous advanced features which overcome the various deficiencies inherent in existing circuit breaker mechanisms, as noted above. This particular circuit breaker mechanism is arranged to be readily adaptable for use with various different types of actuators as desired and also for use with various different sensing means without major modification of the mechanism. in addition, a single-pole assembly incorporating the features of the present invention may readily be combined with other similar assemblies to form a multipole circuit breaker mechanism. The present invention also provides for rapid displacement of the movable contacts by releasing the mechanical connection between the contact element and the remainder of the mechanism when the element is released from the on position, along with the provision of both positive make and also positive break. Additional improvements in detail design of the structural elements of the circuit breaker inechanism of the present invention, effective to overcome the other common deficiencies in known circuit breaker mechanisms, will be pointed out below in connection with the detailed description of the instant invention.

An object of the present invention is the provision of an improved circuit breaker mechanism arranged to provide reliable performance characteristics under severe operating conditions including vibration and shock loads.

Another object is to provide a circuit breaker mechanism which may be released by the application of an extremely small force, yet develops relatively large contact pressure.

A further object of the invention is the provision of a circuit breaker mechanism in which the various parts used are of uncomplicated design and relatively few in number and further characterized by relatively simple circular or linear movement of the moving parts.

Still another object is to provide a circuit breaker mechanism designed to readily accommodate any desired sensing means or combination thereof.

Yet another object of the invention is the provision of a circuit breaker mechanism which allows the alternate use of either a push-pull or toggle type actuator without the requirement for any design change or rework of the mechanism.

An additional object is to provide a circuit breaker mechanism in which all movable parts are either inherently balanced or shaped and pivoted in such a manher that they tend to secure stable positions under adverse operating conditions.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings in which:

Fig. 1 shows a side elevation of a pre erred embodiment of the present invention in the on position,

2 shows a side elevation of the same embodiment of the present invention with the various parts in the positions which they assume immediately after release from the on position by operation of a suitable sensing means,

Fig. 3 is a perspective view of a portion of the same embodiment of the present invention arranged to show bmt in Pig. 3

'iton which it occupies in Fig. 1.

the relationship between concentrically mounted elements of the mechanism, and

Fig. 4 illustrates the same embodiment of the present invention in the ofi position.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, Pig. 1 illustrates a preferred embodiment including a supporting frame 31 which con- 'stitutes a simplified schematic representation of means for as shown, includes a pivotal support 16 fixedly secured to the supporting member 31 and arranged to rotatably support a non-conductive portion 21 fitted with a project- 'ing pin 18 spaced radially of the portion from the pivotal support 16 and arranged to be engaged in a longitudinally extending slot 19 located centrally of an elongated first member 22 mounted for angular displacement about its pivot 26 induced by the angular movement of the pin 18 about the pivotal support 16, which accompanies rotary movement of the portion 20 of the actuator assembly. The manner in which the member 22 is rotatably supported upon the pivot 26 is shown since the pivot 26 is located coaxially with and immediately behind the boss 26 in the posi- The opposite end of the first member 22 is fitted with a projecting pivotal support 28 upon which a second elongated member 30 is pivotally mounted for angular movement relative to the first member 22, said second member 30 being provided at its opposite end with the boss 26'. The second member Bil also includes an elongated projection adjacent to the pivot 28 provided with a slightly curved camming surface 36 extending along one side thereof. A pivotal support 44 projecting from the supporting member 31 rotatably supports an arm 32 having a lateral projection from one end provided with a first camming surface 33 on one side and a second camming surface 46 on the other side, said camming surface 33 being shaped to extend along a constant radius about the pivotal support 44 and arranged to engage the boss 26 to retain said boss in axial alignment with the pivotal support 26 upon which the first member 22 is rotatably mounted. The arm 32 is continuously biased in a counterclockwise direction by biasing means represented by spring 50 in Fig. 1 into engagement with a suitable stop 51 in the position in which armature 32 is shown in Fig. 1, except when a suitable sensing means such as that represented in Fig. l by phantom lines and generally designated by reference numeral 54 becomes effective to momentarily bias the arm 32 in a clockwise direction to move the camming surface 33 out of engagement with the boss 26. The first and second members 22 and 31) respectively are arranged to cooperate in controlling the position of the elongated movable contact assembly including the lever arm 40 rotatably mounted upon a pivotal support 4-3 projecting from the supporting member 31 and fitted at its opposite end with a pin or roller bearing 38 arranged to engage the c amming surface 36 on the elongated projection of the second member extending radially from the pivotal support 28. The movable contact assembly supports a movable contact 53 intermediate its ends for movement into and out of engagement with a stationary contact 52. The contact assembly is continuously biased in a clockwise direction as shown in Fig. 1 about the pivotable J support 43 and toward the stop pin 42 by the compression spring 56 supported upon a suitable bracket 55 secured and the second member 35 about the pivotal support 26 to the supporting member 31. Other details of the structure included in the circuit breaker mechanism comprising the present invention will be identified and described in connection with the following description of the operation of the present invention.

The respective phases of the operation of this device will be discussed in sequence beginning with the establishment of the on position represented by the showing in Fig. l as supplemented by the showing in Fig. 3. As the actuator is moved from the off position shown in Fig. 4 to the on position by rotating the non-conducting portion thereof Ztl in a counterclockwise direction as shown in Fig. 1 against the restraining influence of the spring 35 connected to the stop means 34, the pin 13 travels downwardly about the pivotal support 16 to produce counterclockwise rotation of the first member 22 about its pivotal support 26 and simultaneous counterclockwise rotation of the second member 3t about its boss 26', since the first and second members are pivotally interconnected by the pivotal support 28 which is moved downwardly in slot 2% from the upper end of the slot to the lower end of the slot. It should be noted that the 'slot 2% in the supporting frame 31 is not essential to support the mechanism and may in fact be entirely eliminated. However, it is illustrated in the showings in Figs. 1 through 4 to clearly indicate the nature of the relationship between the first and second members and the nature of the movement of pivotal support 28 relative to the supporting member 31. The counterclockwise rotation of the second member 31 about the boss 26' forces the camming surface 36 against the roller bearing 33 on the end of the movable lever arm 4! in turn forcing the lever arm 40 to rotate in a counterclockwise direction about the pivotal support 43 to bring the movable contact 53 into engagement with the fixed or stationary contact 52. With the contacts in engagement, the spring 56 is increasingly compressed and therefore exerts a powerful biasing effect upon the lever arm ll) tending to rotate said arm in a clockwise direction, said biasing effect being transmitted through roller bearing 38 and camming surface 36 to the second member 3% and thence through the pivotal support 28 to the first member 22 to bias the first member in a clockwise direction about its pivotal support 26. However, the longitudinal slot 19 is so located in member 22 and in relation to the pivotal support 16 that when the pin 13 has reached a position at the extreme right hand end of slot 19 as shown in Fig. 1 its initial movement must be in a downward direction for a short distance. Consequently, the biasing effect exerted by spring 56 in the manner described immediately above overcomes the biasing effect of the spring 35 so that the actuator assembly and particularly the portion 20 thereof remains in the on position as shown in Fig. 1 until it is released either manually or automatically by operation of a suitable sensing means.

The circuit breaker mechanism can readily be placed in the off position illustrated in Fig. 4 by manual movement of the portion 29 of the actuator assembly in the direction of the arrow adjacent thereto in Fig. 1 until it reaches the off position. In order to produce such movement of the actuator assembly it is only necessary to overpower the portion of the biasing eifect of the spring 56 not ofiset by the opposed biasing effect of spring 35 until the pin 18 has traveled clockwise past its lowermost position as it moves to the left along slot 19. Thereafter, the biasing efiect of spring 35 is added to that of spring 56 to insure continued movement of the actuator assembly to the off position during which the continued clockwise movement of the pin 18 is effective to produce simultaneous clockwise rotation of the first member 22 and the coaxially disposed boss 26, respectively, due to the pivotal connection 2% between the respective members,

whereby the camming surface 36 is lifted out of engagement with the roller 38 so that the biasing spring 56 becomes effective to produce rapid clockwise rotationof the movable contact assembly about the pivotal support 43 until it engages the stop means 42. This operation shifts all of the components of the circuit breaker mechanism to the various position shown in Fig. 4 in which they remain until the circuit mechanism is returned manually to the on position in the manner described in detail above.

When the circuit breaker mechanism has been placed in the position shown on Fig. 1, it may also be released from this on position by operation of a suitable sensing means 54, which, as shown in Fig. 1, represents a magnetically operated device sensitive to an electrical overload condition. For example, the sensing means may comprise an electromagnet responsive to an overload condition by generating a magnetic field strong enough to rotate a striker into engagement with the lug projecting from the arm 32 to produce substantial clockwise rotation of the arm 32 about the pivotal support 44 and thereby produce the instantaneous condition shown in Fig. 2 by releasing the boss 26 from engagement with the camming surface 33. When the boss 26 is released from the arm 32, the second member 3%) becomes free to rotate about the pivotal connection 23 until the member 3i"; engages the stop means as shown in Fig. 2. This limited rotation of the member 39 in a counterclockwise direction is induced by the continuous biasing effect of spring 56 operating against the camming surface 36 through the lever arm 4t) and the roller 38 mounted thereon. Very limited counterclockwise angular displacement of the member completely releases the movable contact sembly from engagement with the camming surface 36 and hence from engagement with the remainder of the mechanism ther by permitting rapid movement of the movable contact assembly in response to the biasing effect of spring 56. Meanwhile, the release of boss 26' relieves the first member 22 from the dominant clockwise biasing effect thereon about pivotal support 26 applied by spring as through lever arm 44), roller 38, carnming surface as, and pivotal connection 23. Consequently, the spring 35 is rendered eilective to produce clockwise rotation of the actuator assembly and accompanying clockwise rotation of the first member 22 so that the pivot connection 23 at the left hand end of the member 22 is moved upwardly toward the top of the slot 29. At the same time, the spring 50 tends to effect counterclockwise movement of the arm 32 to return it to the position shown in Fig. 1 immediately after it has been displaced by the sensing means, and concurrently the initial counterclockwise rotation of the second member 30 about the pivot connection 28 into engagement with the stop means 34 stretches the biasing spring 6t) connected at one end thereto and at the other end to pin 63 and thereby creates a biasing effect tending to return the end of member 39 hearing the boss 25 to the position shown in Fig. 1. During this return movement, an early stage of which is illustrated in Fig. 2, the boss 26 engages the upper camming surface id upon the arm 32 to temporarily displace the arm 32 once more in a clockwise direction about the pivotal support 4d against the biasing eltect or" spring 54) while the boss 26' is being displaced downwardly until it is returned to the position in which it is shown in Fig. Thereafter, the arm 32 once again returns to the position in which it is shown in Fig. 1 under the influence of spring Sli. Thus, the series of movements initiated by operation of the sensing means is also eventually efiective to place all of the components of the circuit breaker mechanism in the same positions which they assume when the mechanism is placed in the cit position manually as described above. See Fig. 4 for a showing of the end positions assumed by the various components of the mechanism.

Since all of the parts of the circuit breaker mechanism characterizing the present invention are returned automatically in the manner described above to their original ott position in response to an impulse from the associated overload sensing means .34, the reset phase of operation for this device is completed simply by manually moving the portion 25 of the actuator from its off position shown in Fig. 4- to its on position as shown in Fig. l, with the result described in detail above in regard to the establishment of the on position of the mechanism.

The circuit breaker mechanism of the present invention includes numerous features which contribute significant advantages over the various circuit breaker mechanisms of. the prior Since the actuator assembly is not an ral part of the circuit breaker mechanism, the mechat sm may be used with various different actuator assemblies suited to particular needs. This circuit breaker mechanism is also operationally disassociated from the sing means, so that a single configuration of the circt,.-. breaker mechani m may be used in cooperation with any one of several different sensing means. Whenever the mechan is tripped either manually or automatically by the sensing means, the movable contact assembly is immediately freed from an mechanical engagement with the remai der of the circuit breaker mechanism and is thus caps or"- a quic: -reak and rapid movement away from the fixed contact to interrupt the circuit most effectively. Despite the complete freedom of movement of the movable contact assembly upon tripping, positive make is assured by engagement of the camming surface 36 with the roller bearing 38 when the actuator assembly is moved to the on position, and positive break is assured by engagement of the curved surface 62 with the roller bearing 3% whenever the mechanism is tripped it movable contact 5'3 has become welded to the stationary contact 512. Furthermore, with the provision of positive make and positive break the actuator assembly cannot be made to start or complete its movement between the on and off positions if the contacts should faii to close or open. Accordingly, the position of the portion of the actuator assembly is always a positive reliable indication of the position of the contacts. addition, the configuration of the various components of the present invention is favorable to an extremely desirabie resolution of forces for a circuit breaker mechanic: For example, the relatively large movement arm of the boss 26 about the pivotal connection 23 assures a relatively small bearing load between the 2s and the camming surface 33 in comparison with a relativel large force exerted upon the roller hearing 38 by the bearing surface 3:5 due to the relatively small moment arm of the point of contact with roller 38 about the pivotal connection 28. This desirable relationship and other such relationships between the various correlated members of this circuit breaker mechanism assures the application of a relatively large force tending to maintain contact between the tired contact and the movable contact while relativeiy small forces are required to move the actuator assembly in either direction and to displace the arm 32 by operation of a suitable sensing means.

Aside from the numerous advantages noted above, the present invention is designed so that variations in the construction of the components required are facilitated to meet various design and operating conditions and hence extend the utility of this device. While numerous components of the circuit breaker mechanism comprising the present invention as sh 1 in the accompanying drawings are represented as sir .-plane stampings, many of these parts will actually three-dimensionally formed and arranged to be incorpor' ted in a sandwich type construction of mating or associ tezl components. For example, the planar and 55; may conveniently be constructed in elongated Ll-shaped configurations, one interiitted within the other, and arranged to receive an actuating assembly between the opposed portions of the inner member in a production version of this device. The employment of actuator assemblies other than that illustrated in Figs. 1 through 4 is also facilitated by the construction of the present invention. For example, a so-called pushpull button may be used as the external portion of the manual control in place of the toggle type actuator assembly illustrated. in such a modification, the portion 26 of the actuator assembly as shown would be replaced with alinearly movable button projecting through the envelope enclosing the mechanism and connected at its inner end by means of a suitable lost-motion connection to a rotatable element pivotally supported upon the supporting frame 31 and provided with a projecting pin corresponding to pin 18 for operative engagement in the slot 19 in the member 22. This push-pull button may also be provided with a spring biasing it toward the off position. Thus, this modified actuator assembly is operable to produce on, off, or reset operations identical, in every respect, to those described above in connection with the toggle type actuator assembly shown. This irnproved circuit breaker mechanism is also so constructed that it permits the incorporation of special as well as conventional electrical sensing means such as shunt, calibrating, or relay trip. Additional contact positions for alarm or remote control applications may also be provided within the frame supporting this device. Moreover, the configuration of the circuit breaker mechanism is such that all of the parts may be fabricated using reasonable commercial tolerances and yet not be subjected to undue strain or excessive Wear in use. The production, inspection, assembly and operation of this invention is further facilitated by the fact that all of the moving parts are subiected only to a simple straight line or circular motion. Finally, the various movable parts were designed with special consideration for difficult applications in which the circuit breaker mechanism is exposed to severe shock and vibration as in installations in commercial and military aircraft. Whenever feasible, each moving part was adequately balanced, and where this was not possible, the main mass of such part was concentrated about the pivotal support for that part.

When the teachings of the present invention are applied to a multipole circuit breaker mechanism, a gang release may be provided by incorporating a generally rectangular release means which is pivotally supported intermediate the ends of its opposite sides upon the supporting frame 31 for rotation about an axis parallel to the axis common to the pivot 26 and the boss 26'. The release means should be spring biased so that one edge engages the edge of the member 30 in each component of the multi-pole mechanism. With such an arrangement, displacement of any one of the members 30 due to tripping of the component in which it is incorporated Will rotate the release means about its pivotal axis so that its opposite edge will operatively engage the upper camming surface 46 of all of the arms 32 and thereby simultaneously displace all of the arms to release all of the components of the multi-pole circuit-breaker mechanism.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. it is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A circuit breaker mechanism, the elements of which are movable between an on and an off position, including a fixed frame, first and second susbtantially coextensive elongated members pivotally interconnected at one end and rotatably mounted upon independent pivotal supports at the other end for rotation about a common axis therethrough, the pivotal support for said first elongated member being fixedly secured to said fixed frame, releasable restraining means for the pivotal support for said second elongated member, means located interediate the ends of said first elongated member for operative engagement with a manual actuator mechanism, movable means mounted upon said frame operable in resonse to an overload condition to release'the pivotal support for said second elongated member from said restraining means, movable contact supporting means mounted adjacent said first and second elongated members for movement et: ee its off position and its on position, engaging means secured to said second elongated member adjacent its pivotal connection to said first elongated member, said engaging means being disposed so that the movable contact supporting means will be moved into its on position by the engaging means during colpivotal movement of said first and second members about their pivotal supports in response to operation of a manual actuating mechanism and so that both collective piv 'al movement of said members in the opposite direction in response to operation of a manual actuat- Eng mechanism and release of the pivotal support for said second elongated member will release said movable contact supporting means from its on position by disengaging said engaging means therefrom.

2. A circuit breaker mechanism, the elements of which are movable between an on and an otF position, including first and second substantially coextensive elongated members pivotally interconnected at one end and rotatably mounted upon independent pivotal supports at the other end for rotation about a common axis therethrough, means located intermediate the ends of said first elongated member for operative engagement with a manual actuator mechanism, camming means projecting from said second elongated member adjacent its pivotal connection to said first elongated member, movable .eans operable in response to an overload condition to release the pivotal support for said second elongated member, movable contact supporting means mounted adjacent said first and second elongated members for limited movement between its off position and its on position, said camming means being disposed angularly relative to said second elongated member so that the movable contact supporting means will be moved into its on position by engagement of the camming means therewith during collective pivotal movement of said first and second members about their pivotal supports and so that both collective pivotal movement of said members in the opposite direction and release of the pivotal support for said second elongated member will release said movable contact supporting means from its "011 position by disengaging said camming means therefrom.

3. A circuit breaker operating mechanism, the elements of which are movable between an on position and an ofi position, including first and second substantially coextensive elongated members pivotally interconnected at one end and rotatably mounted upon independent pivotal supports at the other end for rotation about a common axis therethrough, means located intermediate the ends of said first elongated member for operative engagement with a manual actuator mechanism, camming means projecting from said second elongated member adjacent its pivotal connection to said first elongated member, movable means operable in response to an overload condition to release the pivotal support for said second elongated member, a movable contact supporting arm generally disposed at an acute angle relative to said elongated members, a supporting pivot rotatably supporting said arm at the end most remote from said members, follower means mounted upon the end of said arm nearest said members, and limiting means arranged to restrict rotation of said arm to a small angular displacement between its off position and its on position, said camming means being disposed angularly relative to said second elongated memoer so that the movable contact supporting arm will be moved into its on position by engagement of the camming means with the follower means during collective pivotal movement of said first and second members about their pivotal supports and so that both collective pivotal movement of said members in the opposite di- 9 rection and release of the pivotal support for saidsecond elongated member will release said arm from its on position by disengaging said camming means and said follower means.

In a circuit breaker assembly including a supporting frame, a manual actuator assembly mounted upon said frame and movable between an off position and an on position, an overload sensing means mounted upon said frame, a stationary contact fixedly mounted upon said frame, and a movable contact, a circuit breaker operating mechanism comprising a contact supporting means rotatably mounted upon said frame to which the movable contact is fixedly secured, a first elongated member pivotally connected at one end to the frame and operatively engaged intermediate its ends by the actuator assembly, a second elongated member pivotally connected at one end to the other end of said first elongated member and provided at its other end with a boss projecting therefrom disposed so that it may be aligned with the axis about which the first elongated member is rotatably mounted upon the frame, projecting means attached to said second elongated member adjacent its pivotal connection to said first member for engagement with said contact supporting means, and a latch means controlled by the sensing means and arranged to reieasably restrain the second elongated member by engagement with the boss projecting therefrom so that the first and second elongated members rotate together about a common axis in response to movement of the actuator assembly into its on position to engage said contact supporting means with said projecting means and thereby move said contact supporting means into a position in which the movable contact thereon is pressed into engagement with the stationary contact, and rotatable together about the same axis in the opposite direction in response to reverse movement of the actuator assembly to its off position to permit movement of said contact supporting means in the opposite direction so that the movable contact is disengaged from the fixed contact, said latch means being operable in response to an overload sensing means to release said boss so that said second elongated member rotates about its pivotal connection to said first elongated member to disengage said projecting means from the contact supporting means and thereby separate the movable contact from the stationary contact.

5. In a circuit breaker assembly including a supporting frame, a manual actuator assembly at least a portion of which is rotatably mounted upon said frame, an overload sensing means mounted upon said frame, a stationary contact fixedly mounted upon said frame, and a movable contact, a circuit breaker operating mechanism movable between an on position at one extreme and an off position at the other extreme in response to movement of the actuator assembly comprising an elongated contact supporting arm rotatably mounted upon said frame to which the movable contact is fixedly secured intermediate its ends, a first elongated member pivotally connected at one end to said frame provided intermediate its ends with a slot therethrough for sliding engagement with the rotatable portion of the actuating assembly and having a pivotal support projecting from the other end thereof, a second elongated member rotatably mounted at one end upon the pivotal support projecting from the first elongated member and provided at its other end with a boss projecting therefrom disposed so that it may be aligned with the axis about which the first elongated member is rotatable, engagement means attached to said second elongated member adjacent said pivotal support therefor, and a latch means rotatably mounted upon the frame which is controlled by the sensing means and arranged to releasably restrain the second elongated member by engagement with the boss projecting therefrom so that when the operating mechanism is moved to its on position the first and second elongated members move together about a common axis to bias the contact supporting arm into a position in which the movable contact is pressed into engagement with the stationary contact by moving said engagement means into contact with the free end of said elongated contact supporting arm and so that when the operating mechanism is moved to its off position the first and second elongated members move together in the opposite direction about a common axis to disengage said engagement means from said elongated contact supporting arm and thereby release the movable contact from the stationary contact, said latch means being operable in response to an impulse from the overload sensing means to release said boss so that said second elongated member rotates about said pivotal support relative to said first elongated member to disengage said engagement means from said elongated contact supporting arm without prior movement of the operating mechanism to its off position.

6. A device as described in claim 5, and, in addition, a first biasing spring connected at one end to said second elongated member intermediate its ends and at the other end to the frame arranged to bias said second member into engagement with said latch means, a first stop means fixedly secured to the frame and arranged to limit rotary movement of said second member away from said latch means, a second biasing spring connected at one end to said latch means and at the other end to the frame effective to bias said latch means into engagement with the boss projecting from said second member, a second stop means fixedly secured to the frame adjacent said latch means and arranged to limit movement of said latch means in the direction in which it is biased by said second biasing spring, and a third biasing spring supported by the frame and engaging said contact supporting arm intermediate its ends to bias the contact supporting arm and the movable contact attached thereto away from the stationary contact.

7. A device as described in claim 6, in which said latch means comprises an elongated body portion rotatably mounted intermediate its ends upon a pivotal support attached to and projecting from the frame, an elongated projecting portion attached to and extending laterally from one end of said elongated body portion, a first arcuate camming surface formed on the edge of the projecting portion nearest the axis of rotation of the elongated body portion and disposed along a constant radius about the axis of rotation of the body portion, and a second arcuate camming surface formed on the opposite edge of the projecting portion.

8. In a circuit breaker, an operating mechanism movable between an on position and an olf position for both manual and automatic operation, comprising a frame, a first elongated member centrally slotted for engagement with manual control means and pivotally connected at one end to said frame, a second elongated member pivotally connected at one end to the other end of and extending parallel to said first member, a pin extending from the other end of said second member, latch means releasable in response to an overload sensing means and arranged to normally engage and restrain said pin in a position coincident with the pivot axis at said one end of said first member so that said second member pivots with said first member about a common axis in response.

to movement of a manual control means, an arm supporting a movable contact and pivotally connected to said frame for rotation about an axis parallel to the pivot axis of said first member, said arm extending adjacent a fixed contact mounted on said frame and thence to a point adjacent the pivotal connection between said first and second members, a projection extending outwardly from said one end of said second member and having an arcuate cam surface arranged to engage and restrain the free end of said movable contact arm to hold the movable contact supported thereby against the fixed contact when said first and second members are rotated into their on position by means of a manual control means, the pivotal axis of said arm being so disposed angularly in relation to said cam surface that the free end of said arm is released by said cam surface either when the first and second members are moved by a manual control means to their off position or when said pin is released by said latch means in response to a signal from an overload sensing means, and biasing means continually bearing against said arm intermediate its ends to force it out of engagement with the fixed contact whenever the free end of the arm is released by said cam surface.

9. A device as described in claim 8 and, in addition, a stop mounted on said frame and so disposed that it limits the rotational movement of said second member when said pin is released by said latch means, spring biasing means attached intermediate the ends of said second member tending to return said other end of said second member to its normal position with said pin restrained by said latch means, and camming means on said latch means arranged to cooperate with said pin as it returns to its normal position to momentarily displace said latch means.

10. A'device as described in claim 9 in which said latch means comprises, an elongated body portion rotatably mounted intermediate its ends upon a pivotal support attached to and projecting from the frame, an clongated projecting portion attached to and extending laterally from one end of said elongated body portion, and an arcuate camming surface formed on the edge of the projecting portion nearest the axis of rotation of the elongated body portion and disposed along a constant radius about the axis of rotation of the body portion, said camming means being formed on the opposite edge of the projecting portion.

References Cited in the file of this patent UNITED STATES PATENTS 951,852 Smith et a1. Mar. 15, 1910 1,132,772 Harris Mar. 23, 1915 2,150,307 Wulsten Mar. 14, 1939 2,182,038 Soulat Dec. 5, 1939 2,345,105 Dorfman et al. Mar. 28, 1944 2,610,272 Platz Sept. 9, 1952 

